Invasion, Bioenergy, and Natural Enemies of Insect Pests: Ecological and Agricultural Tradeoffs in Two Study Systems
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Invasion, bioenergy, and natural enemies of insect pests: Ecological and agricultural tradeoffs in two study systems A DISSERTATION SUBMITTED TO THE FACULTY OF THE UNIVERSITY OF MINNESOTA BY James O. Eckberg IN PARTIAL FULLFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY Dr. Gregg A. Johnson, Dr. Donald L. Wyse November 2015 Copyright Page James O. Eckberg 2015 © Acknowledgements: I am grateful to numerous faculty, students, staff, family, and friends. I am most grateful to my advisors Gregg Johnson and Don Wyse for their support, encouragement and insight throughout this process. I thank my wife, Elizabeth, and son, Max, for showing me what true happiness looks like and teaching me to balance work and life. I am grateful to my entire committee including Ruth Shaw, David Mulla, and George Heimpel for many engaging conversations, their support, and feedback. I thank many collaborating and supportive faculty including Craig Sheaffer, Ulrike Tschirner, Michael Casler (USDA-ARS), John Luhman, Nick Jordan, Neil Anderson, John Lamb, and Ed Cushing. Matt Bickell, Jerry Holz and Kimon Karelis were very helpful with setting up and maintaining plots. I thank the staff at the Ag and Energy Center (Central Lakes College): Keith Olander, Hannah Barrett, Kent Scheer, and Ron Nelson. I was fortunate to be able to interact and collaborate with many great students, staff, and post-docs. In particular I want to thank Joe Kaser, Jacob Jungers, Mikey Kantar, Bryan Runck, Milan Plećaš, Julie Peterson, Mark Asplen, Matt Kaiser, Laura Seefeldt, Andrew Felton, Rachel Pain, Karen Blaedow, Colin Borsh, Joshua Larson, Kevin Betts, Josh Gamble, Kayla Altendorf, Sergey Berg, Grace Loppnow, Amy Kendig, Justin Meissen, Andrea Hefty, Grace Wilson, Collin Motschke, Mike Kaiser, Tony Charvoz, Andrew Cumming, Emily Beeman, Wally Rich, Mike White, Lynne Medgaarden, and Marilyn Swanson. I thank John and Travis Moncrief and Bob Schafer for introducing me to agricultural sciences. I am grateful to my undergraduate advisor, Pamela Kittelson, for her guidance and patience during my early years in ecology. I would also like to thank numerous family and friends for their support including Kirsten, Peter, Joe, Tiffany, and Mike Eckberg, Katherine and Ralph Baumgartner, Judy Morgan, Tracey, Scott, Laurann, Katie, and Nickie Galowitz i Johnson, Barb and Jerry Galowitz, Timm, Joe, and Chelsey Bockman, and Andy Montain. ii Dedication: I dedicate this dissertation to my grandparents, Olaf and Aleda Kaasa, for their encouragement, support, and wisdom. They continue to be an inspiration in my life. iii Abstract: Agriculture is at the intersection of major global challenges for the 21st century. There is a growing need to increase food security and production. Mounting demand for bioenergy, biomaterials, and naturalized areas for recreation is also placing pressure on food production systems. At the same time, the intensive practices credited for improving production have degraded the environment, eroded ecosystem services and threaten the potential to sustain further increases in yield. There is an incredible need to understand the tradeoffs inherent in diversifying and optimizing farming systems for food and bioenergy production in ways that also support ecosystem services. This thesis explores tradeoffs in two systems. The first is an integrative system that seeks to manage perennial crop bioenergy, natural enemies, and pests. The second is a study of the invasion risk of selectively breeding switchgrass for bioenergy production. In chapter 1, I describe the community of hoverflies (Syrphidae) in soybeans. The original objective of this research was to test the predation and biological of hoverflies in perennial crop-soybean systems. Hoverfly adults in our region feed exclusively on nectar and pollen and the larvae prey only on aphids. Coupling flowering perennial crops adjacent to soybean aphid populations was expected to greater enhance hoverfly populations and biological control of soybean aphid. However, across two years of research hoverflies remained at very low density in soybeans. Upon further evaluation of the literature it became clear that there was little information on the abundance and community composition of hoverflies in soybeans. Therefore, I collaborated to develop a manuscript describing the abundance of hoverflies, their performance on soybean aphid, and the possible ecological causes for their low abundance. iv In chapter 2, I evaluated the spillover of tent caterpillars onto willow bioenergy crops. The prevailing notion is that perennial crops will support natural enemies, yet little information is available on the pests of perennial crops. I developed a manuscript describing the spatial dynamics of tent caterpillar spillover onto willow bioenergy crops. In chapter 3, I tested the natural enemies and bioenergy production of integrative perennial cropping systems. Producing natural and bioenergy crops is a major goal of integrative cropping systems. Yet little information is available on the tradeoffs between crops and cropping structure in terms of supporting natural enemies and producing bioenergy. Across three years I quantified both theoretical ethanol yield and natural enemies in perennial crops and found significant tradeoffs but also some potential synergies in the ability to achieve both of these objectives. In chapter 4, I explore the emerging ecological risk associated with producing switchgrass biomass for bioenergy. This research is critical to better understanding the tradeoff between producing bioenergy and minimizing invasion potential of switchgrass. As a first step to understanding invasiveness in chapter 4, I tested the biomass and competitiveness of switchgrass cultivars and wild populations in the greenhouse. I discuss strategies for minimizing invasiveness while promoting biomass production. In chapter 5, I characterize the germination and dormancy of switchgrass cultivar and wild population as well as the factors contributing to dormancy. Though the focus of this manuscript is primarily on breeding, the implication is that populations with greater germination could have greater emergence in natural areas which, in some situations, may contribute to greater weediness. v These chapters highlight several important ecological and agricultural tradeoffs in integrative perennial agriculture: crop production and weediness, natural enemies, or pests. Such information is important to designing and optimizing agricultural systems for agricultural production in ways that also support ecosystem services. vi Table of Contents List of Tables……………………………………………………………………………viii List of Figures……………………………………………………………………………ix Chapter 1 ………………………………………………………………………………...1 Field Abundance and Performance of Hoverflies (Diptera: Syrphidae) on Aphid Prey: Implications for Biological Control of Soybean Aphid Chapter 2………………………………………………………………………………...24 Spillover of tent caterpillar (Malacosoma americanum) herbivory onto willow bioenergy crops in an agricultural landscape Chapter 3………………………………………………………………………………...43 Biomass Bioenergy and Natural Enemies of Integrative Perennial Cropping Systems Chapter 4………………………………………………………………………………...74 Competitive interactions of cultivar and wild switchgrass with native grasses Chapter 5...……………………………………………………………………………...99 Switchgrass population and cold-moist stratification mediate germination Bibliography……………………………………………………………………………117 vii List of Tables Chapter 1 Table 1…………………………………………………………………………………..19 Toxomerus marginatus avg (± Standard error) larval performance on Aphis glycines, A. nerii, and A. monardae. viii List of Figures Chapter 1 Figures Figure 1 ………………………………………………………………………………..21 Syrphid avg (± standard error) adult abundance across four soybean fields (4 ha per field) Figure 2 ………………………………………………………………………………...22 Syrphid avg (± standard error) larvae and pupae density across four soybean fields Figure 3 ………………………………………………………………………………...23 Syrphid abundance and aphid abundance across four soybean fields ix Chapter 2 Figures Figure 1 ………………………………………………………………………………..39 Map of experimental site showing spatial distribution of willow plots, their defoliation, proximity to the nearest host tree and its defoliation. Figure 2 ………………………………………………………………………………...40 Relationship between host tree defoliation and herbivory on willow. Figure 3 ………………………………………………………………………………...41 The proportion of willow with more than 10% insect defoliation versus proportion of willow surviving to the end of the growing season. Figure 4 ………………………………………………………………………………...42 Insect defoliation on host trees in relation to habitat type and tree size (volume, m3). x Chapter 3 Figures Figure 1 ………………………………………………………………………………....67 Species Composition in polyculture surrounded by willow (closed circles) versus polyculture surrounded by soybeans (open triangles) Figure 2 ………………………………………………………………………………....68 2014 Treatment (alley = polyculture surrounded by willow, polyculture = polyculture surrounded by soybeans) and spatial position (1= interior, 2= edge) effects on total polyculture biomass Figure 3 ………………………………………………………………………………....69 2014 Floral composition. Species level response to treatment and position. Figure 4 …………………………………………………………………………………70 2014 Leaf Area Index Figure 5 ………………………………………………………………………………....71 Biofuel production from 3 years of polyculture and willow production xi Figure 6 ………………………………………………………………………………...72 2014 polyculture (PS, circles) versus SRC willow (WS, triangles). Syrphidae, spiders